Fluid pressure control apparatus



A/Rfl/ Nov. 13, 1945. J BENT 2,389,020

FLUID PRESSURE CONTROL APPARATUS Filed June 30, 1945 Iigl 17 2O 19" 1 1g 55 29 I 54 4 22 16 =fiim|! 25 V IIIIIIIIIIIIIIIHI 25 lllll INVENTOR Arthur J Bent QKMLQZ/ ATTORN EY Patented Nov. 13, 1945 FLUID PRESSURE CONTROL APPARATUS Arthur J. Bent, Wilkinsburg, Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application June 30, 1943. Serial No. 492,839

12 Claims.

This invention relates to fluid pressure control devices and more particularly'to the automatic or self-lapping type.

One object of the invention is the provision of an improved device of the above type.

Another object of the invention is the provision of a device of the above type which is arranged for either individual or joint control from either or both of two control stations, such as the engineers and/or pilots control stations on airplanes or ships.

Another object of the invention is the provision of a device of the above type arranged to be controlled by either or both fluid under pressure and mechanical means.

Another object of the invention is the provision of a device of the above type arranged to be controlled either individually or jointly by fluid under pressure and by manuall operative means and embodying means for substantially counteracting the pressure of fluid supplied thereby so that the manual controlling force is substantially independent of or not-materially influenced by the pressure of fluid supplied by the device.

Still another object of the invention is the provision of a device as defined in any of the above objects in which the movable parts have relatively low frictional resistance to movement so that the device will operate to vary pressure of fluid supplied with a relatively high degree of accuracy in accordance with the degree of controlling forces and slight changes therein.

Other objects and advantages will be apparent from the following more detailed description of the invention,

In the accompanying drawing. Fig. 1 is a vertical sectional view of a control device constructed in accordance with one form of the invention; and Fig. 2 is a view similar to a portion of Fig. 1 embodying a modification of the invention.

Description Referring first to Fig. 1, the improved control device comprises a casing section I having a chamber 2 extending therethrough. One end of this chamber is closed by a flexible diaphragm 3 clamped around its marginal edge between the casing section and a cover member 4 secured to the casing section. The opposite end of chamber 2- is closed by a flexible diaphragm 5 which is clamped around its marginal edge between the casing section and a valve casing B which is se cured to the casing section I. The two diaphragms are thus spaced apart and said diaphragms are also arranged in coaxial relation.

Two followers 1 and 8 are clamped to opposite sides of diaphragm 5 between a collar 9 provided on a member II), which has a sleeve-likeportion ll extending centrally through the two followers and said diaphragm, and a collar I2 provided on a member [3 which has a stud portion extending into and having screw-threaded engagement with the portion ll of member ID. The member I is contained in chamber 2' at one side of diaphragm 5 while member l3 extends through a chamber ill at the opposite side of said diaphragm and a bore in the wall I5 of casing section I' into a chamber 16. The portion of member l3 extending through wall I5 is preferably cylindrical in section and has a free sliding fit therein to facilitate reciprocation with low resistance to movement. The chambers M and 16 are in permanent communication through a choke H.

The member 13 is provided with a through axial bore H! which, at the end opening to chamber I6, is encircled by a valve seat provided for. engagement by a release valve l9 contained in said chamber and which. has a fluted stem 20 extending into said bore. This valve is supported on the end of a fluted stem 2! projecting from a fluid pressure supply valve 22 which is contained in a chamber 23. Chambers l6 and 23 are. separated by a wall 24 and the supply valve stem'is mounted to slide in a bore through said wall, the supply valve being arranged to cooperate witha valve seat provided on said wall around the end of said bore which opens to chamber 23 for controlling communication between said chambers. A spring 25 in chamber 23 acts on the supply valve 22 for urging it to its seated position shown.

Two followers 26 and 21 are clamped centrally to opposite sides of diaphragm 3 between a collar 28 provided on a member 29 which has a sleevelike portion 3!] extending centrally through said diaphragms and follower, and a collar 3| provided on a control member 32 which has screw threaded engagement with sleeve-like portion 30 of member 29. The control member 32 has two oppositely extending stems 33 and 34 arranged in coaxial relation to the diaphragms, the stem 33 extending through chamber 2 at one side of diaphragm 3, while stem 34 extends through a chamber 35 at the opposite side of the diaphragm and thence through a bore in cover 4 to a chamber 36 therein. The portion of the cover through which this bore is provided has an annular groove encircling stem 34 and containing a ring seal 31 engaging the peripheral surface of said stem to prevent leakage of fluid under pressure from chamber 35 to chamber 36. Chamber 35 is in constant communication through a passage 38 with chamber l4.

The member ID secured to diaphragm has a through axial bore aligned with the adjacent enlarged portion of bore ill in member l3 and the end portion of stem 33 is slidably mounted therein. The member ID has an annular recess surrounding stem 34 and containing a ring seal 38a having sealing contact with the peripherial surface of said stem for preventing leakage of fluid under pressure from chamber 2 to bore l8 in mem ber I3, which bore is in permanent communication with the atmosphere through a passage 39 extending through the two stems 33 and 34 and opening to chamber 36 in the cover 4.

A spring 50 in chamber l4 acts against member I 3 to urge same and the diaphragm 5 to their normal positions shown in the drawing, while a. bias spring 49 contained in bore It bears at opposite ends against stem 33 and fluted stem 20 of the release valve l9 to hold said valve against movement upon relative movement of diaphragm 5 to such position.

A coil spring 4| contained in chamber 2 and encircling the stem 33 bears at one end against a follower 44 which is in contact with control member 32, while the opposite end bears against a follower 45 which is in contact with member Ill. With the two diaphragms in the position shown in the drawing the spring 4| is substantially fully expanded.

The chamber 2 is connected to a control pipe 46 which may lead to a controlling means (not shown) located at any desired control station, and which may be of any desired type arranged to supply fluid under pressure to and release fluid under pressure from chamber 2 to provide any desired degree of controlling pressure therein.

For also controlling the device individually or jointly with'th'e control just mentioned, I provide means which may be in the form of a cam 41 and which may be secured to turn with a shaft 48 joumaled in the cover 4. A lever 49 is secured to shaft 48 for turning cam 41.- This cam is arranged with its'peripherial surface for contact ing the end of stem 34, and said surface is so designed that uponmovement of lever 49 in a clockwise direction from a normal position shown in thedrawing, the stem will be displaced in the direction of the diaphragms to a degree dependent upon the extent of such movement. Upon movement of lever'49 in the opposite direction, the stem 34will move in the opposite direction in a manner which will be later brought out, according to the extent of movement of the lever. In other words,'the cam 41 will cause displacement of'stem 34 from its normal position shown a degree corresponding to the distance the lever 49 is out of its normal position shown,

Chamber 23 is arranged to be constantly supplied with fluid under pressure from any suitable source by way of a pipe'5l, while chamber I6 is connected to apipe 52 provided for conveying fluid under pressure to and from any fluid pressure responsive device (not shown) which it may be desired to control.

. Operation Let it be assumedinitially that lever 49 and cam are in the positions shown and that chamber 2 is at atmospheric pressure, under which condition the parts of the control device will assume the positions shown to permit c osu e Q the supply valve 22 by spring 25 and opening of the release valve by spring 40. With the release thus also open to the atmosphere.

If it is now desired to supply fluid under pressure to pipe 52, fluid may be supplied from the one control station through pipe 48 to chamber 2 wherein it acts on diaphragm 5, and when this pressure is increased suflioiently to overcome spring 50 said diaphragm moves or deflects downwardly. This movement is relative to the release valve [9 until the member l3 seats against said valve to close communication between chamber l5 and the atmosphere and further movement is then opposed by the additional pressure of spring 25 on the supply valve 22. When the pressure of fluid is then increased in chamber 2 on diaphragm 5 to asuflicient degree to overcome both springs 50 and 25, said diaphragm deflects further in a downward direction and acts through the release valve l9 to unseat supply valve 22, whereupon fluid under pressure flows from supply pipe 5| past supply valve 22 to chamber l6 and thence to pipe 52. At the same time as fluid under pressure flows to pipe 52 it also flows through choke I! to chamber M to act on-diaphragm 5 in opposition to the pressure of control fluid in chamber 2. Fluid under pressure also flows from chamber M to chamber 35 wherein it acts on diaphragm 3 for reasons which will be later brought out but which are not pertinent to the operation being described. The choke H. is provided to so restrict the supply of fluid under pressure to chambers l4 and 35 as to prevent the pressure increasing in said chambers ahead of the increase in pressure in the device (not shown) supplied with fluid under pressure through pipe 52.

When the pressure of fluid supplied to chamber l4, as above described, is increased to a degree which in cooperation with the force of springs 50 and 25 slightly exceeds theopposing pressure of fluid in chamber 2 acting on diaphragm 5, said diaphragm deflects upwardly and permits spring 25 to seat the supply valve 22 thereby cutting off the supply of fluid under pressure to pipe 52. and limiting the pressure of fluid obtained therein to a degree predetermined bythe pressure of fluid supplied 'to chamber 2. Movement of the diaphragm 5 ceases upon closure of the supply valve 22 due to preventing any further increase in pressure in chamber l4 on said diaphragm and also due to removal of force of spring 25 from said diaphragm, so that the release valve [9 will remain closed to thereby bottle up the fluid under pressure in pipe 52.

If it is desired to increase the pressure of fluid in pipe 52, fluid under pressure may again be supplied through pipe 46 to chamber 2 to increase the pressure of fluid therein acting on diaphragm 5. The device will then operatein the same manner as above described to cause a corresponding increase in pressure of fluid in chamber I6 and pipe 52 and also in chambers I 4 and 35. It will thus be seen that the pressure of fluid in pipe 52 can be increased in such increments as desired by the provision of corresponding increments of control pressure in chamber 2, and amaximum degree of pressure may be provided in said pipe by providing a certain maximum pressure of fluid in said chamber.

While spring 25 acts as above described, its efiect upon pressure of fluid obtained in pipe 52 is negligible on account of its relatively low force with respect to the area of diaphragm 5.

If it is now desired to reduce the pressure of fluid in pipe 52, fluid under pressure is released from chamber 2. When the pressure in chamber 2 acting on one side of diaphragm is thus sufiiciently reduced, with respect to the opposing force on said diaphragm of spring 50 and pressure of fluid in chamber I4, said opposing force deflects said diaphragm in an upwardly direction. Due to the action of the light bias spring 49 in the release valve stem 25, this movement of diaphragm 5 is relative to the release valve I9 and thus opens the vent communication past said valve whereupon fluid under pressure is released from chamber I5 and pipe 52 to the atmosphere. At the same time as the pressure of fluid in pipe 52 is thus reduced, a corresponding reduction in pressure occurs in chambers I4 and 35- by way of choke'l'l, and when the pressure in chamber I4 is thus reduced sufficiently with respect to the control fluid pressure in chamber 2, the latter pressure deflects the diaphragm 5 downwardly until the member I3 engages the release valve I9. This prevents further release of fluid under pressure from pipe 52. thereby limiting the reduction in pressure therein to a degree corresponding to the reduction in pressure of the control fluid acting in chamber 2.

If it is desired to effect a further reduction in pressure in pipe 52, a further reduction in pressure is effected in chamber 2, and the device will then operate to efleot a corresponding reduction in pressure in said pipe in the same manner as above described. Upon a complete release of fluid under pressure from chamber 2, the diaphragm 5 will move to and remain in its normal position to allow a complete release of fluid under pressure from pipe 52.

One purpose of bias spring 50 is to ensure that the diaphragm 5 will move to the position shown upon final release of a relative low control pressure in chamber 2 and then remain in such position to ensure a complete release of fluid under pressure from chamber I4, although it is possible to arrange or design the parts soas not to require a bias spring. The bias spring 50 being constantly effective on diaphragm 5 with pressure of fluid in chamber I4 will always act to limit the pressure in pipe 52 to a degree less than the control pressure in chamber 2 by an amount proportional to its force, but since such force may be of a relatively small degree with respect. to the area of diaphragm, the eflect is negligible. Moreover since the force of the bias spring is constantly effective it in no way interferes with varying the pressure in pipe 52 according to variations in the pressure of the control fluid in chamber.

It will now be seen that the control device is operative in accordance with desired increments of change, either increase or decrease, in pressure of control fluid in chamber 2 to cause corresponding steps of change in pressure in pipe 52, and it will be noted that since the only friction which opposes operation of the device is the relatively small amount which will normally exist between the member I3 and the casing wall I5 and between the stems of the supply and release valves and the Walls of the bores in which they operate, the control pressure will be reproduced with a relatively high degree of fidelity.

Let it now be assumed that it is desired to control the pressure of fluid in pipe 52 solely from the other station, that is by operation of lever 49. Under this condition pipe 46 and chamber 2 will be opened to the atmosphere.

To supply fluid under pressure to pipe 52 by operation of lever 49, said lever is turned in a clockwise direction from its normal position to actuate cam 4'! for displacing the stem 34 in a downwardly direction. This movement of stem 34 is transmitted through spring seat 44 to one end of spring 4| and thence through said spring and seat 45 to members I0 and I3 and diaphragm 5, whereupon saidmembers and diaphragm move in the direction of the release valve I9, the diaphragm 3 incidentally moving with the stem 34. After a certain downward movement of stem 34, the member I3 seats against the release Valve l9 and then further downward movement acts through said valve to open the supply valve 22. Fluid under pressure then flows past the supply valve to chamber I6 and pipe 52 and also to chambers I4 and 35 in the same manner as above described.

When the pressure of fluid thus obtained in chamber I4 acting on one side of diaphragm 5 is increased to a sufiicient degree to overcome the opposing force of spring 4|, it being noted that the opposite end of said spring is held against movement by engagement of stem 34 with cam 47, said diaphragm deflects against said spring and permits movement of the supply valve 22 toward its seat. The supply valve will become seated when the pressure of fluid obtained in pipe 52 is increased to a degree determined by the displacement of the upper end of spring 4| from its normal position shown which displacement determined the force of said spring on said diaphragm upon movement thereof to the position for permitting closure of the supply valve 22. It will thus be seen that the device operates to limit the pressure of fluid obtained in pipe 52 in accordance with the distance the lever 49- is out of the normal position shown in. the drawing.

If it is desired to increase the pressure of fluid in pipe 52. the lever may be moved further from its normal position and the device will operate in the same manner as above described to cause a corresponding increase in pressure of fluid in said pipe. A maximum degree of pressure may be obtained in pipe 52 upon movement of lever 49 to a chosen position a certain maximum distance away from normal position.

If it is desired to reduce the pressure of fluid in pipe 52, the lever 49 is turned in the direction of normal position. This permits pressure of fluid in chamber I4 acting on diaphragm 5 and thence through spring 4| and stem 34 onthe cam 41 to move said diaphragm upwardly to an extent determined by the extent of movement of lever 41. This movement of the diaphragm 5 pulls member I3 out of seating engagement with release valve, IQ whereupon fluid under pressure is released from chamber 16 and pipe 52, and thus from chambers I4 and 35, past said valve to atmosphere.

As the pressure of fluid in chamber I4 isthus reduced, the diaphragm 5 is deflected downwardly by spring 4| in the direction of the release valve 19, and will finally seat against said valve when said pressure is. reduced to the degree correspondin to the force of said spring as determined by the displacement of the upper end of said spring from its normal position shown in the drawing. If it is now desired to effect a further reduction in pressure of fluid in pipe, the

lever 49 is moved further towards its normal position to reduce the degree of displacement of the upper end of spring 4| from its normal position. A corresponding reduction in pressure of fluid in pipe 52 will then occur in the same manner as above described. Upon return of lever 49 to its normal position, a substantially complete expansion of spring 41 is allowed to take place in order that the diaphragm upon movement to the position shown in the drawing may remain therein to provide a complete release of fluid under pressure from pipe 52. The bias spring 59 will act at this time in the same manner and for the same reason as above described.

It will now be seen that the control device will operate to either increase or decrease the pressure of fluid in pipe 52 in such increments as desired as determined by the movement of lever 49, and the pressure obtained in said pipe will be limited in accordance with the distance said lever is out of its normal position and hence the extent of displacement of the upper end of spring 4| from its normal position. It should also be noted that the lever 49 at no time acts to change the pressure of the control spring 4|; it merely acts through said spring to change the position of the diaphragm or to permit a change in position of said diaphragm by pressure of fluid in chamber l4. Further, the device will operate with the fidelity herebefore mentioned to reproduce in pipe 52 fluid at a pressure corresponding to the position of lever 49.

As before mentioned fluid under pressure is supplied to and vented from chamber 35 along with the supply and release of fluid under pressure to and from chamber I4, and the only purpose of this is to provide through the medium of diaphragm 3 a force on the associated end of spring 4| to oppose the pressure of fluid in chamber I4 acting through diaphragm 5 on the opposite end of the spring, so that the force of said spring will be substantially ineffective on cam 41 to oppose or aid manual movement of lever 49. Thus the lever 49 may be moved to any position with substantially the same low degree of force as required to move it out of its normal position at which time the Spring 4| is fully expanded. It is however undesirable to provide equilibrium of opposing forces on the two diaphragms, considering the biasing eifect of spring 59 acting in conjunction with pressure of fluid in chamber [4 on diaphragm 5, since such might result in undesired operation.

For instance, if the friction between member I3 and the casing. wall I5 should become so abnormal with the supply valve 22 open, as to require a higher pressure of fluid in chamber l4 on diaphragm 5 to deflect said diaphragm upwardly against spring 4| than required to deflect diaphragm 3 downwardly against said spring, then the diaphragm 3 would move downwardly and increase the pressure of said spring on diaphragm 5 as the opposing pressure of fluid in chamber l4 increased and thus prevent diaphragm 5 from moving to allow closing of the supply valve 22.

As a result the maximum degree of pressure act-- at least counteracting the maximum de ree of abnormal resistance to movement of member [3 in l in which the two diaphragms 3 and 5 are of substantially the same areas, this biasing force is provided in the spring 50 which therefore serves two functions; namely that of preventing undesired operation such as just described in addition to that of ensuring opening of the release valve l9 to obtain a complete release of fluid under pressure from pipe 52, as above described. If desired however, the diaphragm 3 may be of slightly smaller area than diaphragm 5 as shown to an exaggerated degree in Fig. 2, whereby the opposing pressure of fluid acting on the two diaphragms will provide a differential of forces acting in the direction of cam 41 which at least equals and therefore counteracts the maximum degree of abnormal resistance to movement of member 13 in casing wall H. In the structure shown in Fig. 2, the spring 50, if used, would only have a force sufficient to ensuring opening of the release valve as before described.

Whether the biasing force to avoid the above described undesired operation is obtained by spring 59 as in the structure shown in Fig. 1 or by the use of a smaller diaphragm 3 as in Fig. 2, it will be noted that such force will oppose or aid manual adjustment of lever 49 except for initial movement of said lever out of normal position in the construction shown in Fig. 2 at which time the opposite faces of the two diaphragms will be open to atmosphere and there will be no biasing force. This biasing force is however relatively small and may not even be considered objectionable because it tends to prevent unintended operation of the lever and provides a certain degree of resistance to manual movement which may be desirable. In any case, the lever is never subjected to the major portion of the force developed by pressure of fluid in a chamber l4 on diaphragm 5 and this is very desirable.

In certain control systems it is desirable to control a regulating device or the like jointly from two different control stations. For instance, on certain airplanes powered by two or more engines it is desirable when the speed of the engines are simultaneously controlled by the pilot, that the engineer be capable of adjusting the speed of one or more of the engines in order to synchronize all 'of the engines. The device embodying the invention is particularly adapted for this type of control. For instance, one of these devices may be provided at the engineers control station for controlling 'each engine on the plane. The pipe 46 may lead to the pilots control station where suitable means may be provided for operation by the pilot to supply fluid under pressure to the several pipes 46 simultaneously for thereby efiecting operation of the devices to simultaneously adjust the speed of the several engines. If the engineer then finds it necessary to increase the speed of any one or more engines to bring them into synchronism with the other engine or engines, he then moves lever 49 out of its normal position.

This movement of lever 49 at a time when fluid under pressure from pipe 46 is eifective in chamber 2, and substantially the same pressure of fluid is also efiective in pipe 52 and chamber I4 and 35, causes the device to operate in the same manner as above described to provide in said pipe and chambers fluid at a pressure determined by the position of said lever, this pressure however, being added to that provided in response to pressure of fluid supplied to chamber 2, it being noted that in this case the pressure obtained in pipe 52 is regulated by the combined pressures in chamber 2 of fluid supplied through pipe 46 and of spring 4|. The proper adjustment of lever 49 will therefore provide any desired increase in pressure of fluid in pipe 52 over that obtained in response to pressure of fluid supplied to chamber 2. By such operation of lever 49 it is therefore possible to adjust one means relative to another when both are under a different and common control.

Summary From the above description it will now be seen that I have provided an improved control device capable of individual control from either of two control stations or joint control from both stations. In the illustration one control is by fluid pressure which is particularly useful for control from a remote station, while the other control is local and a manually djustable type. A relatively small degree of manual effort is required for controlling the device regardless of the pressure of fluid supplied by the device, since the device embodies an arrangement which ofisets or counteracts the major portion of the force developed by said fluid pressure in'said device.

Moreover, the device is so constructed that there is a minimum of resistance to movement of the fluid pressure controlling parts whereby the device will vary the pressure of fluid supplied with a relatively high degree of accuracy with respect to the controlling pressure or force, and is thus capable of producing relatively small changes in the pressure of fluid supplied.

Having now described my invention, What I claim as new and desire to secure by Letters Patent is:

1. A control device comprising in combination, a spring, movable abutment means subject to pressure of fluid in one chamber and to opposing pressure of either or both said spring and of fluid in a second chamber and operable to provide fluid in said one chamber at a pressure proportional to said opposing pressure, means providing for varying the pressure of fluid in said second chamber, means adjustable to Vary pressure of said spring on said abutment means, and means subject to pressure of fluid in said one chamber acting on said spring in opposition to pressure of fluid in said one chamber acting on said abutment means.

2. A control device comprising in combination, a movable abutment subject to pressure of fluid in a chamber and to an opposing pressure and movable in one direction upon an increase in said opposing pressure to provide a proportional increase in pressure of fluid in said chamber, and movable in the opposite direction upon a reduction in said opposing pressure to provide a proportional reduction in pressure of fluid in said chamber and movable to a neutral position upon substantial equalization between pressure of fluid in said chamber and said opposing pressure, a spring acting on said abutment, said opposing pressure consisting of pressure of said spring and of fluid in a second chamber, means providing for varying the pressure of fluid in said second chamber, means operable to adjust said spring to provide difierent degrees of pressure on said abutment in the said neutral position thereof, and a movable abutment subject to pressure of fluid in the first named chamber and connected to said spring in opposing relation to the connection between said spring and the first named abutment.

3. A control device comprising in combination, a spring, movable abutment means subject to pressure of fluid in one chamber and to opposing pressure of either or both said spring and of fluid in a second chamber and operable to provide fluid in said one chamber at a pressure proportional to said opposing pressure, means providing for varying the pressure of fluid in said second chamber, means adjustable to vary pressure of said spring on said abutment means, another movable abutment means subject to pressure of fluid in said one chamber and acting on said spring in opposition to pressure of fluid in said one chamber acting on the first named abutment means, both of said abutment means providing substantially the same degree of force against said spring, and another spring under a chosen degree of pressure coacting with pressure of fluid in said one chamber acting on the first named abutment in opposition to pressure of fluid in said one chamber acting on the second named =abutment means.

4. A control device comprising in combination, a spring, movable abutment means subject to pressure of fluid in one chamber and to opposing pressure of either or both said spring and of fluid in a second chamber and operable to provide fluid in said one chamber at a pressure proportional to said opposing pressure, means providing for varying the pressure of fluid in said second chamber, means adjustable to vary pressure of said spring on said abutment means, another movable abutment means subject to pressure of fluid in said one chamber and acting on said spring in opposition to pressure of fluid in said one chamber acting on the first named abutment means, the last named abutment means providing less force opposing force of said'spring than the first named abutment means.

5. A control device comprising in combination, two spaced apart and coaxially aligned flexible diaphragms subject on opposite faces to pressure of fluid in one chamber and subject on adjacent faces to pressure of fluid in a second chamber, a coil spring in said second chamber operatively connected at opposite ends to the two diaphragms, means providing for varying pressure of fluid in said second chamber, one of said diaphragms being movable in one direction by either an increase in pressure of fluid in said second chamber or by said spring to effect a supply of fluid under pressure to said one chamber and being movable in the opposite direction by pressure of fluid in said one chamber either upon a reduction in pressure "of fluid in said second chamber or upon movement of said spring in said opposite direction to release fluid under pressure from said one chamber and being movable to a neutral position upon providing fluid in said one chamber equal substantially to either one or the sum of both the pressure of fluid in said sec- 0nd chamber and/or the pressure of said spring, means operable to move the other diaphragm and associated end of said spring in either one direction or the opposite direction, said diaphragms being of substantially the same areas and therefore operative by pressure of fluid in said one chamber to apply substantially the same degree of pressure to opposite ends of said spring, and a bias spring acting in conjunction with pressure of fluid in said one chamber on said one diaphragm in opposition to pressure of fluid in said one chamber acting on the said other diaphragm.

6. A control device comprising in combination, two spaced apart and coaxially aligned flexible diaphragms subject on opposite faces to pressure of fluid in one chamber and subject on adjacent faces to pressure of fluid in a second chamber, a coil spring in said second chamber operatively donnected at opposite ends to the two diaphragms, means providing for varying pressure of fluid in said second chamber, one of said diaphragms being movable in ne direction by either an increase in pressure of fluid in said second chamber or by said spring to efiect a supply of fluid under pressure to said one chamber and being movable in the opposite direction by pressure of fluid in said one chamber either upon a reduction in pressure of fluid in said second chamber or upon movement of said spring in said opposite direction to release fluid under pressure from said one chamber and being movable to a neutral position upon providing fluid in said one chamber equal substantially to either one or the sum of both the pressure of fluid in said second chamber and/or the pressure of said spring,

means operable to move the other diaphragm and,

associated end of said spring in either one direction or the opposite direction, the said one diaphragm being of greater area than the said other diaphragm to provide a force opposing pressure of said spring which exceeds that provided by the said other diaphragm.

7. A control valve device comprising in combination, means including movable abutment means subject to pressure of fluid in one chamber and to an opposing pressure in a second chamber and operable in accordance with variations in said opposing pressure to effect proportional variations in pressure in' said one chamber, means providing for varying pressure of fluid in said second chamber on said abutment means, pressure exerting means operable to provide other opposing pressure on said abutment means, and means operable by pressure of fluid in said one chamber to substantially counteract the reaction of said pressure exerting means.

8. A control valve device comprising in combination, means including movable abutment means subject to pressure of fluid in one chamber and to an opposing pressure in a. second chamber and operable in accordance with variations in said opposing pressure to effect proportional variations in pressure in said one chamberfmeansproviding for varying pressure of fluid in said second chamber on said abutment means, pressure exerting 'means adjustable to provide other opposing pressure on said abutment means, manual means operable to adjust the pressure of said exerting means, and means subject to the reaction of said exerting means and automatically operable to render said reaction substantially ineffective on said manual means. 7 l a 9. A control valve device comprising in combination, valve means operable to supply fluid under pressure to a first chamber, movable abutment means subject to opposing pressures of fluid in said first chamber and in a second chamber and operable upon an increase in pressure of fluid in said second chamber to effect operation of said valve means, means providing for supply of fluid under pressure to said second chamber, a member operable by force to also effectopera'tion of said valve means, movable means subject to pressure of fluid in said first chamber acting on said member in the direction of action of said force, and manual means operable to apply force to said member.

assaogo 10. A control valve device comprising in combination, valve means operable to supply fluid under pressure to a first chamber, movable abutment means subject to opposing pressure of fluid in said first chamber and in a second chamber and operable upon an increase in pressure of fluid in said second chamber to efiect operation of said valve means, means providing for supply of fluid under pressure to said second chamber, a member operable by force to also eflect operation of said valve means, pressure of fluid in said second chamber being effective on said member in a direction to oppose operation of said member by force and being opposed by pressure of fluid in a third chamber acting on said member, a passage connecting said second and third chambers, and manual means operable to apply force to said member.

11. A control device comprising in combination, movable abutment means subject to opposing pressures of fluid in a first chamber and in a second chamber, valve means operable by said abutment meansin accordance with variations in pressure of fluid in said first chamber to effect proportional variations in pressure of fluid in said second chamber, means providing for varying the pressure of fluid in said first chamber, resilient means in said first chamber acting on said abutment means in opposition to pressure of fluid in said second chamber, movable means operable upon movement to eflect operation of said valve means and cooperative with said resilient means to limit the variation in pressure of fluid in said second chamber effected by said valve means due to movement of said movable means to a degree proportional to the extent of movement of said movable means, force applying means operable to apply force to said movable means for controlling movement thereof, and means operable by pressure of fluid in said second chamber to oppose the reaction of said force on said movable means. 7

. 12. A control device comprising in combination, movable abutment means subject to opposing pressures of fluid in a first chamber and in a second chamber, valve means operable by said abutment means in accordance with variations in pressure of fluid in said first chamber to effect proportional variations in pressure of fluid in said second chamber, means providing for varying the pressure of fluid in said first chamber, resilient means in said first chamber acting on said abutment means in opposition to pressure of fluid in said second chamber, movable means operable upon movement to efiect operation of said valve means and cooperative with said resilient means to limit the variation in pressure of fluid in said second chamber efiected by said valve means due to movement of said movable means to a degree proportional to the extent of movement of said movable means, force applying means operable to apply force to said mov-' able means for controlling movement thereof,

pressure of fluid in said second chamber opposing movement of said movable means by said force applying means, said movable means being subject to pressure of fluid in a third chamber counteracting effect of pressure of fluid in said second chamber, and a passage connecting said second and third chambers.

ARTHUR J. BENT. 

